Water resources data for the 1977 water year for Iowa consists of records of stage, discharge, and water quality of streams; stage, contents, and water quality of lakes and reservoirs; and water levels in wells. This report contains discharge records for 111 gaging stations; stage and contents for 5 lakes and reservoirs; water quality for 21 gaging stations; and water levels for 34 observation wells. Also included are 125 crest-stage partial-record stations, 202 low-flow partial-record stations, and 130 water-quality partial-record stations. Additional water data were collected at various sites, not part of the systematic data-collection program, and are published as miscellaneous measurements and analyses. The data represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating Stage and Federal agencies in Iowa.